Question 35852
Draw a right triangle having an angle of 45 degrees.
The 3rd angle must also be 45 degrees because the 
angles must add up to 180 degrees.
Therefore you have an isosceles right triangle.
The tangent of the 45 degree angle equals the ratio
of the side opposite divided by the side adjacent.
But those are the equal sides of the isosceles rt.
triangle.  Since the sides are equal the ratio is "1".
Therefore the tangent of 45 degrees is "1".
Cheers,
stan H.